Although genetic transmission mechanisms, common to attention deficit hyperactivity disorder (ADHD) and Alzheimer’s disease, are far from being demonstrated, a team of Swiss researchers has just reported an association between these two diseases. , by studying a cohort of more than two million people linked to their biological parents.
Attention deficit disorder withis an infantile behavioral disorder that can persist into adulthood. This affects 5% of children worldwide and 2.5% of adults. It is characterized by inappropriate inattention, impulsivity and motor agitation (hyperactivity). The is a characterized by cognitive impairment, loss of leading to the . It is linked to aging and can appear from the age of 60 ( between 5 and 7% worldwide among people aged 60 and over).
What is the role of heredity in ADHD and Alzheimer’s disease?
Attention deficit hyperactivity disorder (ADHD) is acomplex and many factors contribute to its occurrence. It is an inherited disease and it seems that many intervene in its development. Moreover, the share of in the remains rare with less than 1% of cases linked to a genetic cause (mutation of certain genes of ).
The potential mechanisms of the association between these two pathologies have not been demonstrated, especially as theADHD is difficult even though awareness and knowledge of the disorder has increased in recent years.
The hypothesis of a common inheritance has been put forward, although no joint genetic variant has been demonstrated. However, a 2015 study published insuggests that a nucleotide polymorphism may play a role in the molecular basis of adult ADHD. In addition, these variations would be located in or near genes involved in the processes of
Diagram of nucleotide polymorphism: variation of a single base pair of the genome. © David Eccles, Wikimedia Commons, CC by-sa 4.0
A link between attention deficit hyperactivity disorder and Alzheimer’s disease
A study ofmultigenerational was carried out in Sweden and published this month in . The aim was to examine whether older parents of people with ADHD were diagnosed with dementia. Based on various national registers – reporting births, data on patients and treatments, and deaths – more than 2 million people born between 1980 and 2001, more than 3% of whom were diagnosed with ADHD, have been followed. These people were then linked to their biological parents (parents, grandparents, uncles and aunts) in order to observe the potential family associations between ADHD and .
The authors demonstrate an association between ADHD and Alzheimer’s disease across generations. Relatives of people with ADHD have an increased risk of developing Alzheimer’s disease compared to relatives of people without ADHD. This association declines with the decrease in genetic relatedness (second degree relatives).
Although no causal relationship was demonstrated in this study, mechanisms explaining these associations are suggested by the authors. Genetic variants which have not yet been demonstrated,environmental or health impact caused by ADHD which may in turn promote dementia are all hypotheses made in this study. The researchers also evoke the interest of exploring these different avenues in future research.